There are known devices, such as disk drives, which use different types of recording disks such as optical disks, optical magnetic disks and flexible magnetic disks. Among them, the hard disk drive (HDD) has become so popular as to be one of the indispensable storage devices for today's computer systems. Further, not limited to computers, the hard disk drive is widening its range of application more and more due to the superior characteristics, including movie picture recording/reproducing apparatuses, car navigation systems, cellular phones, and removable memories for digital cameras.
Each magnetic disk used in hard disk drives has a plurality of data tracks formed concentrically. In each data track, a plurality of data sectors are recorded which contain a plurality of servo data including address information and user data. Data can be written to and read from a desired data sector by a head element section which accesses the data sector according to the address information of the servo data.
The head element section is mounted on a slider, which is fixedly attached to the suspension of an actuator. The assembly of the actuator and the head slider is called a head stack assembly (HAS). The assembly of the suspension and the head slider is called a head gimbal assembly (HGA).
The pressure resulting from the viscosity of the air between a slider air bearing surface (ABS) facing a magnetic disk and the rotating magnetic disk balances with the pressure applied by a suspension toward the magnetic disk. This causes the head slider to fly above the magnetic disk at a fixed gap therebetween.
The suspension includes a flexible support member (which is also called flexure or gimbal) which retains the head slider on the side of a magnetic disk-facing surface, and a load beam, which retains the gimbal on the side of the magnetic disk-facing surface. The gimbal is formed deformably so that the slider may incline in a desired direction to accommodate the tilt of the magnetic disk.
The magnetic head slider normally operates at a significantly small flying height above the surface of the high-speed rotating magnetic disk. When it contacts, starts or stops (CSS) for example, the slidable movement of the air bearing surface of the magnetic head slider and the surface of the magnetic head causes static electricity. If static electricity occurs on the magnetic head slider, it may damage the magnetic head element section. To prevent this damage, a conductive adhesive is applied to the boundary face between a lateral face of the magnetic head slider and the gimbal to establish electrical connection between the magnetic head slider and the gimbal.
In general, the conductive adhesive comprises a nonconductive adhesive and a conductive material (filler metal or the like) such as silver mixed therewith. In a severe usage environment concerning temperature, vibration or others, however, the conductive material such as filler metal may drop, which may cause a sliding accident between the magnetic head slider and the magnetic disk. The magnetic head slider is bonded to the gimbal with a normal adhesive (nonconductive adhesive). This adhesive may protrude from the lower portion of the magnetic head slider and reach the terminal of wiring on the gimbal. This may exert a bad influence on the joint between the terminal of the wiring on the gimbal and the terminal of wiring from the magnetic head element section. In particular, the miniaturized magnetic head slider is liable to encounter this event.
To prevent such an occurrence, a conventional gimbal of the magnetic head assembly has been configured as shown in FIG. 10, such that a shield surrounding a conductive adhesive area is provided to prevent the conductive adhesive from being bared. As shown in FIG. 10, in an area 520 on which a magnetic head is mounted, a conductive adhesive 523 is surrounded by a shield 521 so as to prevent failure resulting from drop of the conductive adhesive 523. Incidentally, since having a weak adhesive force, the conductive adhesive 523 is normally applied together with a nonconductive adhesive 512.
Japanese Laid-Open No. 2000-298812 (“Patent Document 1”) discloses a magnetic head assembly having protrusion-preventive walls disposed between a conductive adhesive application area and electrode terminals connected to wiring disposed on gimbal. FIG. 11 is a plan view of an end portion of a flexible support member included in the magnetic head assembly described in Patent Document 1.
As shown in FIG. 11, electrode terminals 506a, 506b, 506c and 506d connected respectively to lines 507a, 507b, 507c and 507d are disposed on gimbal 501 made of a metal material such as SUS304. The electrode terminals 506a, 506b, 506c and 506d are each connected to a corresponding one of electrode terminals of a magnetic head slider (not shown) on the side of the magnetic head element section. Protrusion-preventive walls 505a and 505b are disposed between the electrode terminals 506a, 506b, 506c, 506d and the conductive adhesive application area 502. The conductive adhesive application area 502 is disposed at the almost-center of a magnetic head slider attachment portion 504. A conductive adhesive protrusion-preventive wall 505e is disposed to surround the conductive adhesive application area 502. A nonconductive adhesive application area 503 is disposed around the preventive wall 505e. 
Incidentally, along with the increased amount of information, the recent hard disk drives have been required to promote high-storage capacity, high-performance and miniaturization. Therefore, also magnetic head assemblies themselves have been demanded to have high accuracy, reduced size, and high-reliability. Consequently, fly height concerning read/write performance of a magnetic head has an increased influence on the performance of a product. The fly height-related performance of the product cannot be confirmed until an HGA is actually assembled and subjected to an operation test.
In general, if the operation test shows that a magnetic head slider is defective, it is discarded with a suspension. In order to more decrease cost, it is desired to recover the suspension.
The suspension is designed with emphasis on performance because of HDD performance, improvement in anti-shock performance and adoption of a femtoslider. A thin plate spring (gimbal) attached with a magnetic head slider uses a stainless steel thin plate having a thickness of 15 μm, so that it is easily deformed with external force. If it is intended to recover the suspension by removing the magnetic head slider from the gimbal, it is extremely difficult to recover the suspension because of the deformed gimbal. The major reason is that the shield surrounding the above-mentioned conductive adhesive area makes it hard for a solvent dissolving the adhesive to penetrate thereinto, and therefore, the adhesive force of the adhesive hardly lowers. If the magnetic head slider is intended to be forcibly peeled off, the suspension will bend and thus cannot be recovered. On the other hand, for the configuration of Patent Document 1 described above, since the nonconductive adhesive is applied to the outside of the protrusion-preventive wall, the solvent resolving the adhesive easily penetrates into the nonconductive adhesive, so that it is probable that the suspension may be recovered.
However, the above-described shield or preventive wall (hereinafter, referred to as the spacer) functions as a base which maintains the head slider and gimbal parallel to each other or at a stable angle formed therebetween. That is, it has a function of stabilizing the posture angle of the magnetic head. Further, the spacer has a function in which the thickness of the spacer maintains the thickness of the conductive adhesive to be uniform, thereby reducing variations of resistance values between the slider and the gimbal resulting from the variation of the conducive adhesive.
In particular, a femtoslider, which will become mainstream in the future, imposes increasingly strict requirements on the posture angle of the head. For the specifications of the posture angle as examples, a picoslider with a large-sized slider has a posture angle of +1.2°, whereas some femtosliders need to have a posture angle of +0.40, which is about three times the accuracy for the picoslider.
In short, the suspension needs to be configured to stabilize the posture angle of the head. Since the adhesive area 502 is exposed in the configuration described in Patent Document 1, the solvent easily penetrates the adhesive area 502 at the time of dismantle, which makes it possible to recover the suspension. However, because of the narrow conductive adhesive area, variations in the application positions and amounts of application of the conductive adhesive easily cause the conductive adhesive to run on the preventive wall. In addition, the protrusion of the conductive adhesive poses problems in that not only the posture angle not be controlled, but also the joint with the terminals of the lines from the magnetic head element section is adversely affected.